This invention relates generally to a method and an apparatus for color imaging, and in particular the invention relates to a method and an apparatus for improving the apparent resolution of an electronic color imaging system, for example of the television type.
Arrays of image receiving elements and in particular charge coupled devices (CCD's) are presently used in commercially available products, such as television cameras, for converting a visual image into an ordered sequence of electrical signal amplitudes. In commercial color television, for example, where high quality images are required and where cost is not a significant limiting factor, optical elements split the incoming image and focus it onto three separate CCD arrays. Prior to reaching the CCD arrays, each split image optical signal passes through a filter having a different optical bandpass. Each CCD array then corresponds to and provides an electrical output representative of one of the three required color signals which together generate at the color display apparatus, e.g., a television receiver, the red, green and blue primary color signals which make up the color image. Currently available CCD arrays provide enough resolution so that a three array system can be used in commercial television applications in place of older equipment.
Charge coupled devices however are quite expensive. Thus, many approaches other than a three CCD array system have been tried to tap the consumer market for a solid state, moderate cost television camera. Generally, each moderate cost approach uses a single CCD array masked with an optical filtering element. The filtering element may be, for example, a sequence of stripes or another repeating grid of filter elements having a plurality of different bands of image transmission wavelength ranges. These systems, however, suffer from poor resolution because the three different color signals, which make up the eventually formed color image, result from a single scan of the single CCD array. Therefore the resolution offered by the single CCD array is reduced by a factor of three for each color signal. Various attempts have been made to compensate for this loss of resolution. These corrective schemes however have generally been unsuccessful, often because they merely trade between resolution in the horizontal and vertical directions.
A principal object of this invention is therefore a color imaging camera and method using a single array of photosensitive elements, typically a CCD array, wherein the apparent resolution of the system is substantially identical to the resolution of a system using three such arrays. Other objects of the invention are a method and apparatus for increasing the apparent resolution of a color image which is simple in structure, moderate in cost, reliable, and which provides an aesthetically pleasing, distortion free, output image. Further objects of the invention are an apparatus which uses commercially available components, and which provides output signals compatible with present network television and industry standards.